Surface treatment system and workpiece-holding jig

ABSTRACT

A surface treatment system includes a surface treatment tank, a first guide rail and a second guide rail that extend at a position offset from a position over the upper opening of the surface treatment tank, and a plurality of transfer jigs that respectively hold a workpiece and are supported by the first guide rail and the second guide rail. The transfer jig includes a horizontal arm section, a first guide target section that is guided by the first guide rail, a second guide target section that is guided by the second guide rail, and a vertical arm section that is suspended from the horizontal arm section at a position between the first guide target section and the second guide target section, and holds the workpiece.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application claims priority from and is a divisional application ofU.S. patent application Ser. No. 15/140,869, filed Apr. 28, 2016, whichclaims priority from and is a divisional application of U.S. patentapplication Ser. No. 13/537,862, filed Jun. 29, 2012, now U.S. Pat. No.9,346,632, issued May 24, 2016, and both incorporated by referenceherein, which claims priority from Japanese Patent Application No.2011-145987, filed on Jun. 30, 2011, and Japanese Patent Application No.2012-65564, filed on Mar. 22, 2012.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a surface treatment system (e.g.,serial (continuous) plating system) and a workpiece-holding jig.

Description of the Related Art

A serial plating system that serially (continuously) transfersworkpieces (e.g., circuit boards) in a plating tank has been known as asurface treatment system such as an electroplating system that platesthe surface of a workpiece. The workpiece is suspended from a transferjig that is transferred along a feed rail, and serially transferred inthe plating tank while current is supplied to the workpiece from thefeed rail via the transfer jig. Anodes are disposed in the plating tankon either side of a transfer path of the workpiece (i.e., cathode). Anelectric field is formed between the cathode and the anode toelectrolyze the plating solution and plate the surface of the workpiece.

A structure has been known in which the feed rail extends in parallel tothe longitudinal direction of the plating tank at a position offset froma position above the plating tank (see Japanese Patent No. 3591721)instead of disposing the feed rail above the plating tank (see JapanesePatent No. 3025254). This makes it possible to prevent a situation inwhich dust that occurs when the transfer jig slides on the feed rail ismixed into the plating tank.

A surface treatment system such as a serial plating system is configuredso that a workpiece is suspended from a workpiece-holding jig, andserially transferred in a solution contained in a surface treatmenttank. The workpiece-holding jig normally holds the upper side (end) ofthe workpiece in a suspended state (see JP-A-2009-132956).

The workpiece-holding jig also has a function of setting the workpieceas a cathode with respect to an anode disposed in the surface treatmenttank. An electric field is formed between the cathode and the anode toelectrolyze the plating solution and plate the surface of the workpiece.Therefore, a chuck member that holds the upper side (end) of theworkpiece is formed using a conductive member, and the workpiece is setas the cathode through the workpiece-holding jig.

In Japanese Patent No. 3025254, the transfer jig and the workpiece aresuspended and stably supported right under the feed rail. On the otherhand, when disposing the feed rail at a position offset from a positionabove the plating tank (see Japanese Patent No. 3591721), the center ofgravity of the transfer jig and the workpiece is offset from theperpendicular line that passes through the feed rail, so that anunnecessary moment acts on the transfer jig.

Therefore, the transfer jig disclosed in Japanese Patent No. 3591721 hasa complex structure as compared with the jig disclosed in JapanesePatent No. 3025254 in order to suppress a problem due to an unnecessarymoment. For example, Japanese Patent No. 3591721 provides a removalprevention rail that prevents removal of the transfer jig on the sidesurface of the feed rail. Therefore, the structure of the feed rail alsobecomes complex.

If the workpiece is tilted to intersect the transfer direction whenviewed from above when the workpiece that is held by the transfer jigadvances in the treatment solution, the workpiece may be bent due to thetreatment solution, so that the commercial value of the workpiece may beimpaired. If a vertical motion of the transfer jig occurs when theworkpiece that is held by the transfer jig advances in the treatmentsolution, the electrical contact between the feed rail and the transferjig may be impaired, so that the plating quality may deteriorate. Inorder to prevent such a situation, it is necessary to employ a complexstructure for stabilizing the travel of the transfer jig.

It was also found that it is difficult to ensure the in-plane uniformityof the surface treatment of the workpiece when providing only acurrent-carrying path that is connected to the upper side (end) of theworkpiece (see JP-A-2009-132956).

SUMMARY OF THE INVENTION

Several aspects of the invention may provide a surface treatment systemthat can support a transfer jig in a very stable manner by improving thestructure of a transfer jig that is transferred along a rail disposed ata position offset from a position above a surface treatment tank.

Several aspects of the invention may provide a workpiece-holding jigthat can transfer a workpiece without causing breakage due to liquidpressure or the like even if the workpiece is very thin.

Several aspects of the invention may provide a surface treatment systemin which a feed rail is provided separately from a guide rail, and afeed target section that receives current from the feed rail alwayscomes in contact with the feed rail at a moderate contact pressureindependently of the transfer state of a transfer jig.

Several aspects of the invention may provide a workpiece-holding jig anda surface treatment system that can improve the in-plane uniformity ofthe current distribution of a workpiece, and can further improve thesurface treatment quality of the workpiece.

(1) According to one aspect of the invention, there is provided asurface treatment system comprising:

a surface treatment tank that holds a treatment solution, and has anupper opening;

a first guide rail and a second guide rail that extend along a firstdirection that is parallel to a longitudinal direction of the surfacetreatment tank at a position offset from a position over the upperopening of the surface treatment tank; and

a plurality of transfer jigs that respectively hold a workpiece that isimmersed in the treatment solution contained in the surface treatmenttank, and are supported by the first guide rail and the second guiderail,

each of the plurality of transfer jigs including:

a horizontal arm section that extends along a second direction thatintersects the first direction;

a first guide target section that is supported on one end of thehorizontal arm section, and is guided by the first guide rail;

a second guide target section that is supported on another end of thehorizontal arm section, and is guided by the second guide rail; and

a vertical arm section that is suspended from the horizontal arm sectionat a position between the first guide target section and the secondguide target section, and holds the workpiece.

Specifically, each transfer jig has a doubly supported beamconfiguration in which the first guide target section and the secondguide target section positioned on either side of the vertical armsection (that holds the workpiece) in the second direction are supportedby the first guide rail and the second guide rail. This makes itpossible to stably transfer the workpiece in a horizontal direction bysuppressing occurrence of an unnecessary moment, and suppressing thevertical motion of the transfer jig as compared with the cantileverconfiguration disclosed in Japanese Patent No. 3591721. Moreover, sincethe first guide rail, the second guide rail, the first guide targetsection, and the second guide target section (i.e., sliding sections)are provided at a position offset from a position over the upper openingof the surface treatment tank, it is possible to prevent a situation inwhich dust or the like falls into the surface treatment tank andcontaminates the plating solution.

(2) According to another aspect of the invention, there is provided asurface treatment system comprising:

a surface treatment tank that holds a treatment solution, and has anupper opening;

a first guide rail and a second guide rail that extend along a firstdirection that is parallel to a longitudinal direction of the surfacetreatment tank at a position offset from a position over the upperopening of the surface treatment tank;

a feed rail that extends along the first direction between the firstguide rail and the second guide rail at a position offset from aposition over the upper opening of the surface treatment tank; and

a plurality of transfer jigs that respectively hold a workpiece that isimmersed in the treatment solution contained in the surface treatmenttank, and are supported by the first guide rail and the second guiderail, the plurality of transfer jigs coming in contact with the feedrail, and receiving current from the feed rail,

each of the plurality of transfer jigs including:

a horizontal arm section that extends along a second direction thatintersects the first direction;

a first guide target section that is supported on one end of thehorizontal arm section, and is guided by the first guide rail;

a second guide target section that is supported on another end of thehorizontal arm section, and is guided by the second guide rail;

a vertical arm section that is suspended from the horizontal arm sectionat a position between the first guide target section and the secondguide target section, and holds the workpiece; and

a feed target section that is supported by the horizontal arm section ata position between the guide target section and a vertical arm section,and comes in contact with the feed rail.

According to this aspect of the invention, the surface treatment systemincludes the feed rail in addition to the first guide rail and thesecond guide rail, and the transfer jig further includes the feed targetsection that comes in contact with the feed rail. Since the feed rail isdisposed between the first guide rail and the second guide rail at aposition offset from a position over the upper opening of the surfacetreatment tank, the feed target section of the transfer jig is providedat a position between the first guide target section and the verticalarm section. Therefore, the distance from the vertical arm section tothe first guide target section is longer than the distance from thevertical arm section to the second guide target section. If the secondguide target section is not present, the length of the arm that extendsfrom the first guide target section to the vertical arm sectionincreases, so that an unnecessary moment that acts on the transfer jigincreases. Since the transfer jig has a doubly supported beamconfiguration in which the first guide target section and the secondguide target section are supported by the first guide rail and thesecond guide rail, an unnecessary moment does not act on the transferjig.

(3) According to another aspect of the invention, there is provided aworkpiece-holding jig that holds a sheet-like rectangular workpiece in asolution contained in a treatment tank, the workpiece-holding jigcomprising:

a plurality of first chuck members that hold a first side of therectangular workpiece;

a plurality of second chuck members that hold a second side of therectangular workpiece, the second side being opposite to the first theside in a first direction; and

a frame-like member that is disposed to surround the rectangularworkpiece, and supports the plurality of first chuck members and theplurality of second chuck members,

the frame-like member including:

a first guide section that guides the plurality of first chuck membersso that the plurality of first chuck members are movable along the firstdirection; and

a first biasing member that biases the plurality of first chuck membersin one direction in which the plurality of first chuck members move awayfrom the plurality of second chuck members along the first direction.

The workpiece-holding jig is configured so that at least the pluralityof first chuck members among the plurality of first chuck members andthe second chuck members that hold the opposing sides of the rectangularworkpiece are movable along the first direction. Therefore, tension isalways applied to the rectangular workpiece so that the planarity of theworkpiece can be maintained even if the rectangular workpiece has asmall thickness. This makes it possible to surface-treat each side ofthe rectangular workpiece with a uniform thickness. Moreover, since theplanarity of the workpiece can be maintained without warping even whenthe rectangular workpiece is repeatedly immersed in and removed from thetreatment solution during the surface treatment, it is possible toprevent a situation in which the liquid pressure applied would causewarping. This makes it possible to prevent a situation in which theworkpiece is removed from the chucks, or damaged due to liquid pressure.

(4) According to another aspect of the invention, there is provided asurface treatment system comprising:

a surface treatment tank that holds a treatment solution, and has anupper opening;

a guide rail and a feed rail that extend along a first direction that isparallel to a longitudinal direction of the surface treatment tank at aposition offset from a position over the upper opening of the surfacetreatment tank; and

a plurality of transfer jigs that respectively hold a workpiece that isimmersed in the treatment solution contained in the surface treatmenttank, and are supported by the guide rail, the plurality of transferjigs coming in contact with the feed rail, and receiving current fromthe feed rail,

each of the plurality of transfer jigs including:

a horizontal arm section that extends along a second direction thatintersects the first direction;

a guide target section that is supported on one end of the horizontalarm section, and is guided by the guide rail; and

a feed target section that is supported by the horizontal arm section ata position between the guide target section and a vertical arm section,and comes in contact with the feed rail,

the feed target section including:

a contact section that comes in contact with the feed rail;

a parallel link mechanism that connects the horizontal arm section andthe contact section; and

a biasing member that rotationally biases the parallel link mechanism toapply a contact pressure to the contact section.

According to this aspect of the invention, the feed rail is provided inaddition to the guide rail, and the feed target section that receivescurrent from the feed rail can be caused to always come in contact withthe feed rail at a moderate contact pressure independently of thetransfer state of the transfer jig.

(5) According to another aspect of the invention, there is provided aworkpiece-holding jig that vertically holds a sheet-like rectangularworkpiece in a solution contained in a treatment tank, and sets therectangular workpiece as a cathode, the workpiece-holding jigcomprising:

a frame-like member that is disposed to surround the rectangularworkpiece;

a plurality of conductive first chuck members that are supported by theframe-like member, and hold an upper side of the rectangular workpiece;

a plurality of conductive second chuck members that are supported by theframe-like member in a state in which the plurality of second chuckmembers are electrically insulated from the plurality of first chuckmembers, and hold a lower side of the rectangular workpiece;

a first current-carrying section that supplies current to the pluralityof first chuck members; and

a second current-carrying section that supplies current to the pluralityof second chuck members.

According to this aspect of the invention, the workpiece is held in avertical state by holding the upper side and the lower side of theworkpiece in order to prevent a situation in which it is impossible tomaintain the suspended state of the workpiece due to liquid pressureparticularly when subjecting a very thin workpiece to surface treatment.When the frame-like member, the first chuck members, and the secondchuck members are electrically connected, the resistance of thecurrent-carrying path that reaches the lower frame member that supportsthe second chuck members is inevitably higher than the resistance of thecurrent-carrying path that reaches the upper frame member that supportsthe first chuck members. When holding only the upper side (end) of theworkpiece using the holding jig, the current-carrying path is limited tothe upper frame member. Therefore, the flow of current from the anode tothe workpiece and the frame-like member via the treatment solution (orthe flow of current in the reverse direction) more easily occurs on theupper side of the workpiece that is held by the workpiece-holding jig,so that the in-plane current distribution of the workpiece becomesnon-uniform. The in-plane uniformity of the current distribution of theworkpiece affects the surface treatment quality of the workpiece.According to this aspect of the invention, the first chuck members andthe second chuck members are electrically insulated, and current issupplied to the first chuck members and the second chuck members throughthe first current-carrying section and the second current-carryingsection, respectively. Therefore, the resistance and the current valueof the first current-carrying path from the first current-carryingsection to the first chuck members, and the resistance and the currentvalue of the second current-carrying path from the secondcurrent-carrying section to the second chuck members, can be setindependently. This makes it possible to improve the in-plane uniformityof the current distribution of the workpiece, and further improve thesurface treatment quality of the workpiece.

(6) In the workpiece-holding jig as defined in (5),

the frame-like member may include:

a conductive upper frame member that supports the plurality of firstchuck members;

a conductive lower frame member that supports the plurality of secondchuck members;

two insulating members that are provided on either end of the upperframe member; and

two conductive vertical frame members, an upper end of the two verticalframe members being respectively supported by the two insulatingmembers, and a lower end of the two vertical frame members beingconnected to either end of the lower frame member,

the first current-carrying section may supply current to the upper framemember, and

the second current-carrying section may supply current to the twovertical frame members.

In this case, the first current-carrying section supplies current to thefirst chuck members via the upper frame member, and the secondcurrent-carrying section supplies current to the second chuck membersvia the two vertical frame members and the lower frame member. Since theupper frame member and the two vertical frame members are electricallyinsulated by the two insulating members, the resistance and the currentvalue of each current-carrying path can be set independently.

(7) The workpiece-holding jig as defined in (6) may further comprise:

a common current-carrying section that supports the frame-like membervia part of the first current-carrying section, and supplies current tothe first current-carrying section and the second current-carryingsection.

According to the above configuration, the conductive member provided asthe transfer section among the functional sections (transfer section andworkpiece-holding section) of the workpiece-holding jig can be used asthe common current-carrying section, and the common current-carryingsection can be used as a support section that supports the frame-likemember, so that the number of parts can be reduced.

(8) In the workpiece-holding jig as defined in (7),

the first current-carrying section may include:

an insulating section that is secured on the common current-carryingsection;

a conductive connection section that connects the insulating section andthe upper frame member; and

at least one upper frame current-carrying cable that connects the commoncurrent-carrying section and the connection section, and

the second current-carrying section may include a first vertical framecurrent-carrying cable and a second vertical frame current-carryingcable that connect the common current-carrying section and the twovertical frame members.

According to the above configuration, since the first current-carryingsection includes the insulating section that is secured on the commoncurrent-carrying section, and the conductive connection section thatconnects the insulating section and the upper frame member, the firstcurrent-carrying section can be used as a support section that supportsthe frame-like member together with the current-carrying section, sothat the number of parts can be reduced. The current-carrying paths fromthe common current-carrying section can be separately provided using theat least one upper frame current-carrying cable, the first verticalframe current-carrying cable, and the second vertical framecurrent-carrying cable.

(9) In the workpiece-holding jig as defined in (8),

the connection section may include:

a first vertical arm section and a second vertical arm section thatconnect the insulating section and the upper frame member;

a first protrusion section that protrudes from the first vertical armsection; and

a second protrusion section that protrudes from the second vertical armsection, and

the at least one upper frame current-carrying cable may include a firstupper frame current-carrying cable that connects the commoncurrent-carrying section and the first protrusion section, and a secondupper frame current-carrying cable that connects the commoncurrent-carrying section and the second protrusion section.

When providing the first protrusion section and the second protrusionsection in addition to the first vertical arm section and the secondvertical arm section having a connection function, the first protrusionsection and the second protrusion section may be allowed to function asa redundant section that increases the current-carrying path of thefirst current-carrying section, or may be formed of a material thatdiffers from the material that forms the first vertical arm section andthe second vertical arm section. More specifically, one of the firstvertical frame current-carrying cable and the second vertical framecurrent-carrying cable (i.e., second current-carrying section) and oneof the two vertical frame members form a current-carrying path betweenthe common current-carrying section and the lower frame member. Sincethe vertical frame member is relatively long, and must be reduced incross-sectional area in order to reduce the weight, the vertical framemember has a relatively high resistance. Therefore, the firstcurrent-carrying section is provided with a relatively high resistanceusing one of the first vertical arm section and the second vertical armsection and one of the first protrusion section and the secondprotrusion section so that a balance with the relatively high resistanceof the vertical frame member is achieved. If a balance with therelatively high resistance of the vertical frame member can be achieved,it is possible to use cables that are identical in length andcross-sectional area of the current-carrying section as the first upperframe current-carrying cable, the second upper frame current-carryingcable, the first vertical frame current-carrying cable, and the secondvertical frame current-carrying cable. This makes it possible to reducethe frequency of erroneous installation.

(10) In the workpiece-holding jig as defined in any one of (7) to (9), aresistance of a current path from the common current-carrying section tothe upper frame member and a resistance of a current path from thecommon current-carrying section to the lower frame member may be set tobe substantially equal.

This makes it possible to improve the in-plane uniformity of the currentdistribution of the workpiece, and further improve the surface treatmentquality of the workpiece.

(11) In the workpiece-holding jig as defined in any one of (6) to (10),each of the two insulating members may include a guide section thatslidingly guides an upper end of either of the two vertical frame memberin a vertical direction. According to the above configuration, theweight of the two vertical frame members, the lower frame member, andthe second chuck members is applied to the lower end of the workpiecethat is supported by the first chuck members on the upper end, so thatthe workpiece can be held (maintained) in a vertical state due totension. Therefore, deformation of the workpiece is prevented even ifthe liquid pressure in the surface treatment tank is applied to theworkpiece.

(12) The workpiece-holding jig as defined in (11) may further include abiasing member that biases either of the two vertical frame member thatis slidingly guided by the guide section in a downward direction.According to the above configuration, the biasing force of the biasingmember is applied to the lower end of the workpiece that is supported bythe first chuck members on the upper end in addition to the weight ofthe vertical frame members, the lower frame member, and the second chuckmembers, so that the workpiece can be held (maintained) in a verticalstate due to additional tension.

(13) In the workpiece-holding jig as defined in (12), a lower end of thebiasing member may be secured on either of the two vertical framemembers that is slidingly guided by the guide section, an upper end ofthe biasing member may be secured on a conductive stationary member thatis supported by either of the two insulating members, and either of thefirst and second vertical frame current-carrying cables may be connectedto the stationary member. The first and second vertical framecurrent-carrying cables thus supply current to the vertical frame membervia the stationary member and the biasing member. Alternatively, thefirst and second vertical frame current-carrying cable may be connecteddirectly to the vertical frame member.

(14) According to another aspect of the invention, there is provided asurface treatment system comprising:

a surface treatment tank that holds a treatment solution, and has anupper opening;

the workpiece-holding jig as defined in any one of the above (5) to (13)that holds a workpiece that is immersed in the treatment solutioncontained in the surface treatment tank in a suspended state, and setsthe workpiece as a cathode; and

an anode that is disposed in the surface treatment tank at a positionopposite to the workpiece.

(15) According to another aspect of the invention, there is provided asurface treatment system comprising:

a surface treatment tank that holds a treatment solution, and has anupper opening;

a workpiece-holding jig that holds a workpiece that is immersed in thetreatment solution contained in the surface treatment tank in asuspended state, and sets the workpiece as a cathode;

an anode that extends in the surface treatment tank in a verticaldirection, and is disposed at a position opposite to the workpiece; and

a relay current-carrying section that supplies current to the anode at aposition lower than a liquid surface of the treatment solution containedin the surface treatment tank.

According to this aspect of the invention, current supplied from therelay current-carrying section flows through the anode in the upwarddirection and the downward direction from the contact position of therelay current-carrying section when flowing toward the workpiece (i.e.,cathode) through the treatment solution contained in the surfacetreatment tank. Therefore, current flows through the workpiece toimplement an improved (uniform) current distribution in the verticaldirection.

(16) In the surface treatment system as defined in (15),

the workpiece-holding jig may include:

a frame-like member that is disposed to surround the workpiece;

a plurality of conductive first chuck members that are supported by theframe-like member, and hold an upper side of the workpiece;

a plurality of conductive second chuck members that are supported by theframe-like member in a state in which the plurality of second chuckmembers are electrically insulated from the plurality of first chuckmembers, and hold a lower side of the workpiece;

a first current-carrying section that supplies current to the pluralityof first chuck members; and

a second current-carrying section that supplies current to the pluralityof second chuck members.

According to the above configuration, it is possible to improve thein-plane uniformity of the current distribution of the workpiece, andfurther improve the surface treatment quality of the workpiece due tothe effects achieved by (5) and (14).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view illustrating a surfacetreatment system according to one embodiment of the invention;

FIG. 2 is a partial enlarged view of the surface treatment systemillustrated in FIG. 1;

FIG. 3 is a perspective view illustrating a transfer jig;

FIG. 4 is a view illustrating two guide rails and a transfer jig;

FIG. 5 is a plan view illustrating a transfer jig;

FIG. 6 is a front view illustrating a transfer jig;

FIG. 7 is a view illustrating an anode current control system;

FIGS. 8A and 8B are views illustrating gradual current decrease controlwhen a workpiece exits from a plating tank unit, and gradual currentincrease control when a workpiece enters a plating tank unit;

FIG. 9 is a partial enlarged view illustrating a frame-like member of aworkpiece-holding jig;

FIG. 10 is a view illustrating a state in which a workpiece is held bymoving a movable plate downward;

FIG. 11 is a view illustrating a state in which tension is applied to aworkpiece by supporting the workpiece using a first chuck member;

FIG. 12 is a view illustrating the details of a feed target section;

FIG. 13 is a front view illustrating a current-carrying section and aworkpiece-holding section of a workpiece-holding jig according toanother embodiment of the invention;

FIG. 14 is a side view illustrating the workpiece-holding jigillustrated in FIG. 13;

FIG. 15 is a view illustrating an insulating member that guides avertical frame member, and a biasing member that biases the verticalframe member;

FIG. 16 is a schematic view illustrating an anode that is disposed in atreatment tank illustrated in FIG. 1;

FIG. 17 is a view schematically illustrating the current-carryingsection and the workpiece-holding section of the workpiece-holding jigillustrated in FIG. 13;

FIG. 18 is a view schematically illustrating a method that measures thecurrent distribution of a workpiece;

FIG. 19 is a view illustrating contact points of a workpiece and ananode; and

FIGS. 20A and 20B are views illustrating the current distribution of aworkpiece held by the workpiece-holding jig illustrated in FIG. 6 andthe current distribution of a workpiece held by the workpiece-holdingjig illustrated in FIG. 13.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Exemplary embodiments of the invention are described in detail below.Note that the following exemplary embodiments do not in any way limitthe scope of the invention defined by the claims laid out herein. Notethat all elements of the following exemplary embodiments should notnecessarily be taken as essential elements of the invention.

1. Outline of Surface Treatment System

FIG. 1 is a vertical cross-sectional view illustrating a surfacetreatment system (e.g., serial (continuous) plating system). A serialplating system 10 illustrated in FIG. 1 is configured so that aplurality of transfer jigs 30A that respectively hold a workpiece 20(e.g., circuit board) are transferred (circulated) in the directionperpendicular to the sheet. FIG. 1 illustrates two linear transfer paths110 and 120 that form a circulating transfer path 100 and are parallelto each other. The linear transfer paths 110 and 120 are connected atboth ends to form the loop-like circulating transfer path 100.

The circulating transfer path 100 is provided with a plating tank(surface treatment tank in a broad sense) 200 in which the workpiece 20held by each transfer jig 30A is subjected to surface treatment (e.g.,plating), a mounting section (not illustrated in FIG. 1) that isprovided on the upstream side of the plating tank 200 in the circulatingtransfer path 100 and mounts the untreated workpiece 20 on each transferjig 30A, and a removal section (not illustrated in FIG. 1) that isprovided on the downstream side of the plating tank 200 in thecirculating transfer path 100 and removes the treated workpiece 20 fromeach transfer jig 30A.

In one embodiment of the invention, the plating tank 200 is providedalong the second linear transfer path 120, and the mounting section andthe removal section are provided in the first linear transfer path 110.The circulating transfer path 100 is also provided with a pretreatmenttank group 230 that is disposed on the upstream side of the plating tank200, and a post-treatment tank group (not illustrated in FIG. 1) that isdisposed on the downstream side of the plating tank 200.

The pretreatment tank group 230 includes a degreasing tank, a hot rinsetank, a rinse tank, a shower tank, an acid cleaning tank, and the likethat are sequentially disposed from the upstream side between themounting section and the plating tank 200. The post-treatment tank groupincludes a shower tank and a rinse tank that are sequentially disposedfrom the upstream side between the plating tank 200 and the removalsection. Note that the number and the types of tanks included in thepretreatment tank group 230 and the post-treatment tank group may beappropriately changed.

2. Transfer Jig and Two Guide Rails

As illustrated in FIG. 1, the serial plating system 10 includes theplating tank (surface treatment tank in a broad sense) 200 that holds aplating solution (treatment solution in a broad sense) and has an upperopening 201. As illustrated in FIG. 2 (enlarged view), the serialplating system 10 also includes a first guide rail 130 and a secondguide rail 140 that extend along a first direction (i.e., the directionperpendicular to the sheet) that is parallel to the longitudinaldirection of the plating tank 200 at a position offset from a positionover the upper opening 201 of the plating tank 200. A plurality oftransfer jigs 30A respectively hold the workpiece 20 that is immersed inthe treatment solution contained in the plating tank 200, and aresupported by the first guide rail 130 and the second guide rail 140.

As illustrated in FIGS. 3 to 5, each transfer jig 30A includes ahorizontal arm section 300, a first guide target section 310, a secondguide target section 320, and a vertical arm section 330. As illustratedin FIGS. 3 and 5, the horizontal arm section 300 includes a firsthorizontal arm 300A and a second horizontal arm 300B that extend along asecond direction B that perpendicularly intersects (intersects in abroad sense) the first direction (transfer direction) A, for example. Asillustrated in FIG. 4, the first guide target section 310 is supportedon one end of the horizontal arm section 300, and is guided by the firstguide rail 130. As illustrated in FIG. 4, the second guide targetsection 320 is supported on the other end of the horizontal arm section300, and is guided by the second guide rail 140. As illustrated in FIGS.3 and 6, the vertical arm section 330 includes a first vertical arm 330Aand a second vertical arm 330B that are suspended from a support plate331 secured on the horizontal arm section 300, and hold the workpiece 20at a position between the first guide target section 310 and the secondguide target section 320.

Specifically, each transfer jig 30A has a doubly supported beamconfiguration in which the first guide target section 310 and the secondguide target section 320 positioned on either side of the vertical armsection 330 (that holds the workpiece 20) in the second direction B aresupported by the first guide rail 130 and the second guide rail 140.Therefore, the workpiece 20 can be stably held and transferred bysuppressing the vertical motion of the transfer jig 30A during transferas compared with the cantilever configuration disclosed in JapanesePatent No. 3591721. Moreover, since the first guide rail 130, the secondguide rail 140, the first guide target section 310, and the second guidetarget section 320 (i.e., sliding sections) are provided at a positionoffset from a position over the upper opening 201 of the plating tank200, it is possible to prevent a situation in which dust or the likefalls into the plating tank 200 and contaminates the plating solution.

3. Transfer Jig, Two Guide Rails, and Feed Rail

The plating system 10 is configured so that the workpiece 20 is used asa cathode, and the plating tank 200 is provided with cylindrical meshbags (receiving sections) 202 and 203 that are positioned on either sideof the transfer path of the workpiece 20, and respectively hold anodes(e.g., copper anode balls) 410R and 410L. An electric field is formedbetween the cathode and the anode to electrolyze the plating solutionand electroplate the workpiece 20. Therefore, it is necessary to supplycurrent to the workpiece 20 during transfer. For example, at least oneof the first guide rail 130 and the second guide rail 140 may be used asa feed rail in order to supply current to the workpiece 20. In thiscase, the members of the transfer jig 30A that form a path that suppliescurrent to the workpiece 20 from the first guide rail 130 and the secondguide rail 140 may be formed of an electrical conductor.

In one embodiment of the invention, the plating system 10 includes afeed rail 210 in addition to the first guide rail 130 and the secondguide rail 140 (see FIGS. 1 and 2). As illustrated in FIG. 2, the feedrail 210 includes a plurality of (e.g., four) split feed rails 210A to210D that are insulated from each other in order to implement thecurrent control method disclosed in JP-A-2009-132999. Each transfer jig30A includes a feed target section 340 that comes in contact with one ofthe split feed rails 210A to 210D and receives current (see FIGS. 2 to5). The feed target section 340 is disposed at a position between thefirst guide target section 310 and the vertical arm section 330.

Specifically, each transfer jig 30A has a doubly supported beamconfiguration in which the first guide target section 310 and the secondguide target section 320 positioned on either side of the feed targetsection 340 in the second direction B are supported by the first guiderail 130 and the second guide rail 140. This makes it possible to stablymaintain contact between the feed target section 340 and the feed rail210 when transferring the transfer jig 30A by suppressing the verticalmotion of the feed target section 340.

4. Current Control Method that Utilizes Split Feed Rail

The current control method disclosed in JP-A-2009-132999 is describedbelow with reference to FIGS. 7, 8A, and 8B. Note that the plating tank200 illustrated in FIG. 1 has a length equal to or more than about 10 min the transfer direction perpendicular to the sheet, for example. FIG.7 illustrates a plating tank unit 200A. The plating tank 200 illustratedin FIG. 1 is formed by connecting a plurality of plating tank units200A.

Power supply units 400A to 400D supply current to the workpieces 20during transfer through the corresponding split feed rails 210A to 210D.The power supply units 400A to 400D can supply current to the workpieces20 having one side Fl and the other side Fr via constant current controlat a preset current value (A/dm²). The power supply units 400A to 400Dgradually increase the amount of current when the workpiece 20 istransferred to the plating tank unit 200A, and gradually decrease theamount of current when the workpiece 20 is removed from the plating tankunit 200A.

The plating tank unit 200A illustrated in FIG. 7 can simultaneouslytransfer N (e.g., three) workpieces 20 (20A to 20C or 20B to 20D) in thetransfer direction A in a completely immersed state using the transferjigs 30A (30A1 to 30A4). Note that the term “completely immersed state”used herein refers to a state in which at least the entirety of theplating target surface (side) (i.e., the side Fl and the other side Frillustrated in FIG. 10) of the workpiece 20 is immersed in a platingsolution Q contained in the plating tank unit 200A (see FIGS. 1 and 2).Therefore, (N+1) (i.e., four) workpieces 20 (20A to 20D) are immersed inthe plating solution Q contained in the plating tank unit 200A when theworkpiece 20A exits from an exit 200B of the plating tank unit 200A, andthe workpiece 20D enters an inlet 200F of the plating tank unit 200A.

In this case, the workpieces 20B and 20C are in the completely immersedstate, and the workpieces 20A and 20D are in a partially immersed state.Note that the term “partially immersed state” used herein refers to astate in which only part of the plating target surface (side) (i.e., theside Fl and the other side Fr illustrated in FIG. 10) of the workpieces20A and 20D in the lengthwise (longitudinal) direction is immersed inthe plating solution Q contained in the plating tank unit 200A. The areaof the workpiece positioned outside the plating tank unit 200A isdisposed in the adjacent plating tank unit 200A or another treatmenttank.

When the number of workpieces 20 that can be simultaneously transferredin the plating tank unit 200A in the completely immersed state is N(e.g., N=3), the number of split feed rails 210 and the number of powersupply units 400 are (N+1) (=4).

As illustrated in FIG. 7, the left and right anodes (copper anode balls)410L and 410R that extend in the first direction A and are opposite toeach other are disposed in the plating tank unit 200A (plating solutionQ). The anodes 410L and 410R are common to each workpiece 20 (20A to20D) held by each transfer jig 30A (30A1 to 30A4). The interval(electrode-electrode distance) between the anodes 410L and 410R and eachworkpiece 20 during transfer is maintained at a constant value (givenvalue).

The power supply units 400A to 400D can change the current valuecorresponding to each workpiece 20 held by the transfer jig 30A, and canperform constant current control at a preset current value Is (A/dm²).

More specifically, the power supply units 400A to 400D are configured toperform constant current control in a period in which the workpiece 20is transferred within the plating tank unit 200A in the completelyimmersed state, gradually increase the amount of current when theworkpiece 20A enters the plating tank unit 200A in the partiallyimmersed state, and gradually decrease the amount of current when theworkpiece 20D exits from the plating tank unit 200A in the partiallyimmersed state. The workpiece 20 that is in the partially immersed statein two adjacent plating tank units 200A is subjected to gradual currentdecrease control in the downstream-side plating tank unit 200A, and issubjected to gradual current increase control in the upstream-sideplating tank unit 200A.

As illustrated in FIG. 8A, the amount of current (Iin) is graduallyincreased in proportion to the time (treatment area) when the workpiece20 enters the plating tank unit 200A in the partially immersed state(period T12 (=t1 to t2)) until a preset current value Is is reached. Theworkpiece 20 is subjected to constant current control at the presetcurrent value Is when the workpiece 20 has been completely immersed(t2). The workpiece 20 is subjected to gradual current decrease controlinstead of constant current control at the preset current value Is whenthe workpiece 20 exits from the plating tank unit 200A in the partiallyimmersed state (period T34 (=t3 to t4) (see FIG. 8B). The amount ofcurrent (Idg) is gradually decreased in inverse proportion to the time(treatment area).

According to the above configuration, since the serial plating processcan be performed using the current value set corresponding to eachworkpiece 20, a uniform high-quality coating having a uniform thicknesscorresponding to the current value can be formed on each workpiece 20.

5. Details of Transfer Jig

5.1. Feed Target Section

The feed target section 340 provided to each transfer jig 30A used inone embodiment of the invention comes in contact with one of the N splitfeed rails 210A to 210D. A plurality of transfer jigs 30A illustrated inFIG. 7 include first to Nth transfer jigs 30A1 to 30A4 in which the feedtarget section 340 is attached to the horizontal arm section 300 at adifferent position among N positions in the second direction B. Thefirst to Nth transfer jigs 30A1 to 30A4 respectively come in contactwith an arbitrary split feed rail among the N split feed rails 210A to210D.

According to one embodiment of the invention, the transfer jigs 30A areformed using common parts, and respectively come in contact with anarbitrary split feed rail among the split feed rails 210A to 210D. Asillustrated in FIG. 3, each transfer jig 30A (first to Nth transfer jigs30A1 to 30A4) includes a support section (e.g., support plate 350) thatsupports the feed target section 340. The support plate 350 includes N(N=4) attachment sections 351 to 354 (e.g., threaded holes) that areprovided at a different position in the second direction B.

The feed target section 340 of each transfer jig 30A (first to Nthtransfer jigs 30A1 to 30A4 illustrated in FIG. 7) includes a contactsection 341 that comes in contact with the feed rail 210 (split feedrails 210A to 210D). The contact section 341 is attached to one(attachment section 351 in FIG. 3) of the N attachment sections 351 to354 using a thumb screw, for example. The first to Nth transfer jigs30A1 to 30A4 can be provided using common parts by attaching the contactsection 341 to one attachment section selected from the N attachmentsections 351 to 354.

FIG. 12 illustrates the details of the feed target section 340. The feedtarget section 340 includes a four-bar linkage parallel link mechanism342 that links the support plate 350 and the contact section 341 usingparallel links 342A and 342B, for example. The links 342A and 342B arealways biased in the clockwise direction using torsion coil springs 343(i.e., biasing members). This makes it possible to cause the contactsection 341 to come in contact with the feed rail 210 at a moderatecontact pressure.

The parallel links 342A and 342B are tilted so that the upper fulcrumprecedes the lower fulcrum. In other words, the longitudinal directionof the links 342A and 342B intersects the transfer direction A at anacute angle. Therefore, since the contact section 341 is pulled by thetransfer jig 30A, the contact section 341 travels stably. For example,when the contact section 341 that is vertically guided by two verticalshafts is vertically biased in the downward direction using two springswithout using the parallel link mechanism 342, the contact section 341is tilted if the pressing force due to the springs is unbalanced. Inthis case, the corner of the contact section 341 comes in contact withthe feed rail 210, so that the contact section 341 abnormally wearsaway. According to one embodiment of the invention, the contact section341 comes in contact with the feed rail 210 in a state in which thecontact section 341 is disposed horizontally due to the parallel linkmechanism 342. This makes it possible to prevent a situation in whichthe contact section 341 is tilted so that the corner of the contactsection 341 comes in contact with the feed rail 210. Therefore, abnormalwear and connection failure of the contact section 341 are prevented,and the lifetime of the contact section 341 (expendable) can beincreased.

Note that the configuration of the feed target section 340 illustratedin FIG. 12 may be applied to a surface treatment system that includesthe feed rail 210 in addition to the guide rails 130 and 140. Thesurface treatment system may include only one guide rail and only onefeed rail. When using the guide rail as the feed rail, the feed targetsection significantly wears away due to excessive pressure applied tothe feed target section, so that the lifetime of the feed target sectiondecreases. According to one embodiment of the invention, the feed targetsection 340 can be caused to come in contact with the feed rail 210 at amoderate contact pressure independently of the travel of the transferjig 30A. This makes it possible to increase the lifetime of the contactsection 341 even if the feed target section 340 is formed of brass orthe like.

5.2. First Guide Target Section and Second Guide Target Section

The first guide rail 130 that guides the first guide target section 310includes an upper side, a first side surface, and a second side surfaceopposite to the first side surface in a cross section perpendicular tothe longitudinal direction. The first guide rail 130 is formed in arectangular shape, for example.

The first guide target section 310 that is guided by the first guiderail 130 may include a first roller 311 that comes in rolling contactwith the upper side of the first guide rail 130, a second roller 312that comes in rolling contact with the first side surface of the firstguide rail 130, and a third roller 313 that comes in rolling contactwith the second side surface of the first guide rail 130. The secondguide target section 320 may include a fourth roller 321 that comes inrolling contact with the upper side of the second guide rail 140. Thefirst roller 311 and the fourth roller 321 respectively come in contactwith the upper side of the first guide rail 130 and the upper side ofthe second guide rail 140 on either side of the transfer jig 30A in thesecond direction B, so that the transfer jig 30A can stably travel in ahorizontal state. Since the second roller 312 and the third roller 313hold the side surfaces of the first guide rail 130, it is possible toprevent a situation in which the transfer jig 30A is displaced in thesecond direction B.

5.3. Continuous Transfer Driver Section

A continuous transfer driver section 150 illustrated in FIG. 2 isprovided corresponding to each section obtained by dividing the firstlinear transfer path 120 (see FIG. 1). The continuous transfer driversection 150 includes pushers 153A and 153B that respectively have linearguides 152A and 152B that move along a fixed guide plate 151. Thepushers 153A and 153B are independently moved by a motor (notillustrated in FIG. 2). The transfer jig 30A is continuously andlinearly driven by the pushers 153A and 153B within one section. Thepushers 153A and 153B respectively have a specific drive region and acommon drive region within one section. More specifically, the pusher153 presses the transfer jig 30A in the upstream-side specific driveregion. The pusher 153B succeeds the pusher 153A when continuouslytransferring the transfer jig 30A in the common drive region. The pusher153A moves forward by a given stroke in the specific drive region andthe common drive region, moves backward to the previous position, andtransfers the subsequent transfer jig 30A. The pusher 153B operates inthe same manner as the pusher 153A.

The pushers 153A and 153B respectively have nail members 154A and 154Bthat press a first press target section 360 of the transfer jig 30A. Thenail members 154A and 154B press the first press target section 360 ofthe transfer jig 30A when the pushers 153A and 153B move forward. Thenail members 154A and 154 B can be displaced so as not to hinder theforward movement of the first press target section 360 when the pushers153A and 153B move backward. Note that the transfer jig 30A includes asecond press target section 362 that is used when the workpiece is notcontinuously transferred in the plating tank 20.

5.4. Hook Section

As illustrated in FIGS. 1 to 5, each transfer jig 30A includes hooksections 370 for suspending the transfer jig 30A. As illustrated in FIG.1, the serial plating system 10 further includes a lift section 160 thatengages the hook sections 370, and moves the workpiece 20 held by thetransfer jig 30A upward and downward relative to the plating tank 200.

This makes it unnecessary to use a vertical rail when moving theworkpiece upward and downward outside the plating tank 200, and makes itpossible to reduce the driving force.

5.5. Vertical Arm Section and Workpiece-Holding Jig

As illustrated in FIGS. 3 and 6, the vertical arm section 330 includesthe vertical arms 330A and 330B, for example. The workpiece-holding jig500 is suspended from the vertical arms 330A and 330B.

The workpiece-holding jig 500 is suitably used to hold a very thinworkpiece 20 having a thickness of 100 micrometers or less, andpreferably 60 micrometers or less. In one embodiment of the invention,the thickness of the workpiece 20 is 40 micrometers (=0.04 mm), forexample.

As illustrated in FIGS. 3 and 6, the workpiece-holding jig 500 includesa plurality of first chuck members 510 that hold a first side (e.g.,upper side) 20 a of a rectangular workpiece 20, a plurality of secondchuck members 520 that hold a second side 20 b of the rectangularworkpiece 20 opposite to the first side in a third direction (verticaldirection) C, and a frame-like member 530 that is disposed to surroundthe rectangular workpiece 20, and supports the first chuck members 510and the second chuck members 520.

As illustrated in FIGS. 9 to 11, the frame-like member 530 includes aguide section 540 that guides the first chuck members 510 so that thefirst chuck members 510 are movable in the third direction C, and a coilspring 550 (i.e., biasing member) that biases the first chuck members510 in a direction C1 in which the first chuck members 510 move awayfrom the second chuck members 520 along the first direction.

As illustrated in FIGS. 10 and 11, the frame-like member 530 includes astationary plate 531, and a movable plate 532 that is disposed tooverlap the stationary plate 531. The guide section 540 has a long hole533 that is formed in one (e.g., movable plate 532) of the stationaryplate 531 and the movable plate 532, and extends in the third directionC, and a shaft (e.g., bolt shaft 534) that is formed on the other of thestationary plate 531 and the movable plate 532, and is inserted into thelong hole 533. The coil spring 550 presses (biases) the movable plate532 in the direction C1 relative to the stationary plate 531.

A configuration common to the first chuck members 510 and the secondchuck members 520 is described below with reference to FIGS. 10 and 11taking the first chuck member 510 as an example. The first chuck member510 includes a stationary member 511 that comes in contact with thefirst side Fl of the workpiece 20, and a movable member 512 that isdisposed at a position opposite to the stationary member 511 so as tocome in and out of contact with the second side Fr of the workpiece 20,and is pressed against the second side Fr. The movable member 512 mayinclude a driven element 512A that is driven when the movable member 512is not pressed against the second side Fr, a pressed element 512B thatis always pressed toward the stationary member via a hinge 513 due tospring pressure when the driven element 512A is not driven, and apressing element 512C that is formed in the shape of a thin plate at thefree end of the pressed element 512B.

When attaching the workpiece 20 to the workpiece-holding jig 500, thesecond side 20 b of the workpiece 20 is held using the second chuckmembers 520. When holding the first side 20 a of the workpiece 20 usingthe first chuck members 510, the movable plate 532 is moved downward tothe position (state) illustrated in FIG. 10 against the biasing force ofthe coil spring 550. In this case, the pressed element 512B is set to anopen state (see FIG. 10) by driving the driven element 512A of eachfirst chuck member 510. The driven element 512A is then released, sothat the first side 20 a of the workpiece 20 is held by the first chuckmembers 510. The downward pressing force applied to the movable plate532 is then canceled. As a result, the movable plate 532 moves upwarddue to the biasing force of the coil spring 550, and applies tension tothe workpiece 20, so that the planarity of the workpiece 20 can bemaintained.

Note that tension may be applied to the workpiece 20 using at leasteither the first chuck members 510 or the second chuck members 520.Specifically, the second chuck members 520 may have the abovetension-applying structure.

The workpiece-holding jig 500 having the above structure may be used fora batch process that simultaneously immerses a plurality ofworkpiece-holding jigs 500 in the treatment solution. In this case, thefirst chuck members 510 and the second chuck members 520 may be disposedon the right side and the left side instead of the upper side and thelower side.

5.6. Current-Carrying Section and Workpiece Holding Section Illustratedin FIG. 3

As illustrated in FIG. 3, the current-carrying section of theworkpiece-holding jig 30A includes the conductive horizontal arm section300, the conductive support plate 331, and the conductive vertical armsections 330A and 330B (330). A workpiece-holding section 500 issuspended from the vertical arms 330A and 330B.

As illustrated in FIG. 3, the workpiece-holding section 500 includes aplurality of conductive first chuck members 510 that hold the upper side20 a of the rectangular workpiece 20, a plurality of conductive secondchuck members 520 that hold the lower side 20 b of the rectangularworkpiece 20 opposite to the upper side 20 a in the vertical directionC, and a frame-like member 530 that is disposed to surround therectangular workpiece 20, and supports the first chuck members 510 andthe second chuck members 520.

The frame-like member 530 includes a conductive upper frame member 531that supports a plurality of first chuck members 510, a conductive lowerframe member 532 that supports a plurality of second chuck members 520,and two conductive vertical frame members 533 and 534 that connecteither end of the upper frame member 531 and either end of the lowerframe member 532.

The frame-like member 530 illustrated in FIG. 3 is thus configured sothat the upper frame member 531 and the lower frame member 532 areelectrically connected via the vertical frame members 533 and 534. Thevertical arm sections 332A and 332B that function as a current-carryingsection are electrically connected to the lower frame member 532 via theupper frame member 531. Therefore, the resistance of thecurrent-carrying path that reaches the lower frame member 532 isinevitably higher than the resistance of the current-carrying path thatreaches the upper frame member 531. Accordingly, the workpiece 20 has acurrent distribution with poor in-plane uniformity in which the currentvalve increases as the distance from the upper side 20 a decreases, anddecreases as the distance from the lower side 20 b decreases.

6. Modification of Workpiece-Holding Section of Workpiece-Holding Jig

6.1. First Chuck Member, Second Chuck Member, First Current-CarryingSection, and Second Current-Carrying Section

FIGS. 13 and 14 illustrate a workpiece-holding jig 30B according to oneembodiment of the invention. FIGS. 13 and 14 illustrate aworkpiece-holding section 600 having a configuration differing from thatof the workpiece-holding jig 30A illustrated in FIG. 3. Note that thetransfer section 300 illustrated in FIG. 3 can be used in common to theworkpiece-holding jig 30A illustrated in FIG. 3 and theworkpiece-holding jig 30B according to one embodiment of the invention.The workpiece-holding jig 30B illustrated in FIG. 13 differs from theworkpiece-holding jig 30A illustrated in FIG. 3 as to the structure ofthe workpiece-holding section 600 including a current-carrying section650.

The workpiece-holding section 600 illustrated in FIG. 13 includes aplurality of conductive first chuck members 610 that hold the upper side20 a of the rectangular workpiece 20, a plurality of conductive secondchuck members 620 that hold the lower side 20 b of the rectangularworkpiece 20, a frame-like member 630 that is disposed to surround therectangular workpiece 20, and supports the first chuck members 610 andthe second chuck members 620, and the current-carrying section 650 thatincludes a first current-carrying section 660 and a secondcurrent-carrying section 670.

The first chuck members 610 and the second chuck members 620 areelectrically insulated. The first current-carrying section 660 suppliescurrent to the first chuck members 610. The second current-carryingsection 670 supplies current to the second chuck members 620.

When subjecting a very thin workpiece to surface treatment, it may bedifficult to maintain the suspended state of the workpiece 20 due toliquid pressure when placing the workpiece 20 in the surface treatmenttank 200 by moving the workpiece 20 downward, or when transferring theworkpiece 20 in the surface treatment tank 200 in the transfer directionA (see FIG. 3).

Since the workpiece-holding section 600 according to one embodiment ofthe invention holds the upper side 20 a and the lower side 20 b of theworkpiece 20, it is possible to maintain the workpiece 20 in a verticalstate even if liquid pressure is applied. The distance between the firstchuck members 610 and the second chuck members 620 may be fixed. Notethat the second chuck members 620 may be movable in the verticaldirection, and may be vertically biased in the downward direction usinga biasing member (described later).

The workpiece-holding section 600 according to one embodiment of theinvention can prevent deformation of a very thin workpiece 20 having athickness of 100 micrometers or less, and preferably 60 micrometers orless. In one embodiment of the invention, the thickness of the workpiece20 is 40 micrometers (=0.04 mm), for example. Since theworkpiece-holding section 500 illustrated in FIG. 3 includes the firstchuck members 510 and the second chuck members 520, theworkpiece-holding section 500 can also prevent deformation of theworkpiece 20.

However, when the frame-like member 530, the first chuck members 510,and the second chuck members 520 are electrically connected as describedabove (see FIG. 3), the resistance of the current-carrying path thatreaches the lower frame member 532 that supports the second chuckmembers 520 is inevitably higher than the resistance of thecurrent-carrying path that reaches the upper frame member 531 thatsupports the first chuck members 510. This is because thecurrent-carrying path that reaches the lower frame member 532 passesthrough the current-carrying path that reaches the upper frame member531. When holding only the upper side (end) of the workpiece using theholding jig (see JP-A-2009-132956), the current-carrying path is limitedto the upper frame member. Therefore, the flow of current from the anodeto the workpiece and the frame-like member via the treatment solution(or the flow of current in the reverse direction) more easily occurs onthe upper side of the workpiece that is held by the workpiece-holdingjig, so that the in-plane current distribution of the workpiece becomesnon-uniform. The in-plane uniformity of the current distribution of theworkpiece affects the surface treatment quality of the workpiece.

The workpiece-holding section 600 according to one embodiment of theinvention is configured so that the first chuck members 610 and thesecond chuck members 620 are electrically insulated, and current issupplied to the first chuck members 610 and the second chuck members 620through the first current-carrying section 660 and the secondcurrent-carrying section 670, respectively. Therefore, the resistance ofthe current-carrying path from the first current-carrying section 660 tothe first chuck members 610 and the resistance of the current-carryingpath from the second current-carrying section 670 to the second chuckmembers 620 can be set independently. This makes it possible to improvethe in-plane uniformity of the current distribution of the workpiece 20,and further improve the surface treatment quality of the workpiece 20.

6.2. Frame-Like Member and Current-Carrying Section

The frame-like member 630 of the workpiece-holding section 600 accordingto one embodiment of the invention may include a conductive upper framemember 631 that supports the first chuck members 610, a conductive lowerframe member 632 that supports the second chuck members 620, twoinsulating members 640A and 640B that are provided on either end of theupper frame member 631, and two conductive vertical frame members 633and 634, the upper end of the vertical frame members 633 and 634 beingrespectively supported by the insulating members 640A and 640B, and thelower end of the vertical frame members 633 and 634 being connected toeither end of the lower frame member 632.

In this case, the first current-carrying section 660 supplies current tothe first chuck members 610 via the upper frame member 631. The secondcurrent-carrying section 670 supplies current to the second chuckmembers 620 via the vertical frame members 633 and 634 and the lowerframe member 632. Since the upper frame member 631 and the verticalframe members 633 and 634 are electrically insulated by the insulatingmembers 640 and 640B, the resistance of each current-carrying path canbe set independently.

The current-carrying section 650 may utilize horizontal arm sections 301(301A, 301B) of the transfer section 300 as a common current-carryingsection that supplies current to the upper frame member 631 and thelower frame member 632. The first current-carrying section 660 suppliescurrent to the first chuck members 610 from the common current-carryingsection 301 (301A, 301B) via the upper frame member 631. The secondcurrent-carrying section 670 supplies current to the second chuckmembers 620 from the common current-carrying section 301 (301A, 301B)via the vertical frame members 633 and 634 and the lower frame member632.

The workpiece-holding jig 30A includes the transfer section 300 and thecurrent-carrying section 330. The horizontal arm section 301 (301A,301B) provided as the conductive member 300 may be used as the commoncurrent-carrying section. Moreover, since the common current-carryingsection 301 (301A, 301B) can be used as a support section that supportsthe frame-like member, the number of parts can be reduced.

In this case, the first current-carrying section 660 may include aninsulating section 661 that is secured on the common current-carryingsection 301 (301A, 301B), a conductive connection section 662 thatconnects the insulating section 661 and the upper frame member 631, andat least one upper frame current-carrying cable 663 that connects thecommon current-carrying section 301 (301A, 301B) and the connectionsection. The second current-carrying section 670 may include a firstvertical frame current-carrying cable 671A and a second vertical framecurrent-carrying cable 671B that connect the common current-carryingsection 301 (301A, 301B) and the vertical frame members 633 and 634,respectively.

According to the above configuration, the conductive member provided asthe transfer section 300 among the functional sections (transfer section300 and workpiece-holding section 600) of the workpiece-holding jig 30Bcan be used as the common current-carrying section 301 (301A, 301B), andthe common current-carrying section 301 (301A, 301B) can be used as asupport section that supports the frame-like member 630, so that thenumber of parts can be reduced. Moreover, since the firstcurrent-carrying section 660 includes the conductive connection section662 that connects the insulating section 661 secured on the commoncurrent-carrying section 301 (301A, 301B) with the upper frame member631, the first current-carrying section 660 can also be used as asupport section that supports the frame-like member 630. Therefore, thenumber of parts can be reduced. The current-carrying paths from thecommon current-carrying section 301 (301A, 301B) can be separatelyprovided using at least one upper frame current-carrying cable 663, thefirst vertical frame current-carrying cable 671A, and the secondvertical frame current-carrying cable 671B.

The connection section 662 may include a first vertical arm section 662Aand a second vertical arm section 662B that connect the insulatingsection 661 and the upper frame member 631, a first protrusion section664A that protrudes from the first vertical arm section 662A, and asecond protrusion section 664B that protrudes from the second verticalarm section 662B. In this case, at least one upper framecurrent-carrying cable 663 may include a first upper framecurrent-carrying cable 663A that connects the horizontal arm section301A (one of the common current-carrying sections) and the firstprotrusion section 664A, and a second upper frame current-carrying cable663B that connects the horizontal arm section 301B (the other of thecommon current-carrying sections) and the second protrusion section664B.

When providing the first protrusion section 664A and the secondprotrusion section 664B in addition to the first vertical arm section662A and the second vertical arm section 662B having a connectionfunction, the first protrusion section 664A and the second protrusionsection 664B function as a redundant section that increases thecurrent-carrying path of the first current-carrying section 660. Morespecifically, one of the first vertical frame current-carrying cable671A and the second vertical frame current-carrying cable 671B (i.e.,second current-carrying section 670) and one of the vertical framemembers 633 and 634 form a current-carrying path between the commoncurrent-carrying section 301 and the lower frame member 632. Since thevertical frame member 632 is relatively long, and must be reduced incross-sectional area in order to reduce the weight, the vertical framemember 632 has a relatively high resistance. Therefore, the firstcurrent-carrying section 660 is provided with a relatively highresistance using one of the first vertical arm section 662A and thesecond vertical arm section 662B and one of the first protrusion section664A and the second protrusion section 664B so that a balance with therelatively high resistance of the vertical frame member 632 is achieved.If a balance with the relatively high resistance of the vertical framemember 632 can be achieved, it is possible to use cables that areidentical in length and cross-sectional area of the current-carryingsection as the first upper frame current-carrying cable 663A, the secondupper frame current-carrying cable 663B, the first vertical framecurrent-carrying cable 671A, and the second vertical framecurrent-carrying cable 671B. This makes it possible to reduce thefrequency of erroneous installation.

The resistance of the current path from the common current-carryingsection 301 to the upper frame member 631 and the resistance of thecurrent path from the common current-carrying section 301 to the lowerframe member 632 can be made substantially equal by utilizing theworkpiece-holding section 600 and the current-carrying section 650having the above structure. This makes it possible to improve thein-plane uniformity of the current distribution of the workpiece 20, andfurther improve the surface treatment quality of the workpiece 20.

6.3. Structure that Maintains Workpiece in Vertical State

As illustrated in FIG. 15, each of the insulating members 640A and 640Bmay include a guide section 642A that slidingly guides an upper end 633Aor 634A of the vertical frame member 633 or 634 in the verticaldirection. According to the above configuration, the weight of thevertical frame members 633 and 634, the lower frame member 632, and thesecond chuck members 620 is applied to the lower end of the workpiece 20that is supported by the first chuck members 610 on the upper end, sothat the workpiece 20 can be held (maintained) in a vertical state dueto tension. Therefore, deformation of the workpiece 20 can be preventedeven if liquid pressure is applied to the workpiece 20 in the surfacetreatment tank.

Each of the insulating members 640A and 640B may include a stationarysection 641 that is secured on either end of the upper frame member 631,and a tubular body 642 that is secured on the stationary section 641,and a hole 642A may serve as the guide section that slidingly guides theupper end 633A or 634A of the vertical frame member 633 or 634 in thevertical direction. Note that the stationary section 641 and the tubularbody 642 may be integrally formed. The stationary section 641 mayinclude a vertical element 641A that is secured on the upper framemember 631, and two horizontal elements 641B and 641C, for example. Thetubular body 642 may be secured on the vertical element 641A and thehorizontal element 641B right under the horizontal element 641B. Aflange 633B or 634B provided on the upper end 633A or 634A of thevertical frame member 633 or 634 comes in contact with the horizontalelement 641B (i.e., lower-limit stopper). A clearance 6 is formedbetween the flange 633B or 634B and the horizontal element 641B duringnormal use in which the workpiece 20 is held. The workpiece 20 is heldin a vertical state due to the weight of each member as long as theclearance 6 is formed.

As illustrated in FIG. 15, a biasing member (e.g., compression coilspring 643) that biases the vertical frame member 633 or 634 that isslidingly guided by the guide section 642A in a downward direction D,may be further provided. According to the above configuration, thebiasing force of the biasing member 643 is applied to the lower end ofthe workpiece 20 that is supported by the first chuck members 610 on theupper end in addition to the weight of the vertical frame members 633and 634, the lower frame member 632, and the second chuck members 620,so that the workpiece 20 can be held (maintained) in a vertical statedue to additional tension.

The lower end of the biasing member 634 may be secured on the flange633B (634B) of the vertical frame member 633 or 634 that is slidinglyguided by the guide section 642A, for example.

The upper end of the biasing member 643 is secured on a conductivestationary member 644 that is supported by the horizontal element 641Cof the insulating member 640A (640B). The vertical framecurrent-carrying cable 671A (671B) may be connected to the stationarymember 644.

The vertical frame current-carrying cable 671A (671B) thus suppliescurrent to the vertical frame member 633 (634) via the stationary member644 and the biasing member 643.

As illustrated in FIG. 15, the stationary member 644 may include a bolt644A, a nut 644B, and two metal washers 644C and 644D, for example. Thevertical frame current-carrying cable 671A (671B) is fastened and heldbetween the head of the bolt 644A and the washer 644C at a positionabove the horizontal element 641C. The upper end of the compression coilspring 643 is fastened and held between the nut 644B and the washer 644Dat a position right under the horizontal element 641C. The verticalframe current-carrying cable 671A (671B) and the biasing member 643 arethus secured and electrically connected.

Note that the vertical frame current-carrying cable 671A (671B) may beconnected directly to the vertical frame member 633 (634) without usingthe stationary member 644 and the biasing member 643. For example, aliquid surface Q1 (see FIG. 16) of the treatment solution Q ispositioned between the upper side 20 a of the workpiece 20 and the upperframe member 631 (see FIG. 13). The vertical frame current-carryingcable 671A (671B) may be connected directly to the vertical frame member633 (634) at a position above the liquid surface Q1. In this case, thebiasing member (compression coil spring) 643 illustrated in FIGS. 13 to15 may be disposed between the horizontal element 641 and the flange633B (634B), and need not form a current-carrying path.

7. Anode that Improves in-Plane Uniformity of Current Distribution ofWorkpiece

FIG. 16 schematically illustrates the anode (anode) 410R (410L) that isdisposed on either side of the transfer path of the workpiece 20 (seeFIG. 1). Current is supplied to the anode 410R (410L) from an anode bar400 that extends along the longitudinal direction of the treatment tank200. The anode 410R (410L) is normally connected directly to the anodebar 400. In one embodiment of the invention, however, the anode 410R(410L) is secured on the anode bar 400 in a state in which an insulator430 is interposed between the anode bar 400 and the anode 410R (410L). Arelay current-carrying section 420 is suspended from the anode bar 400.A contact member 420A at the lower end of the relay current-carryingsection 420 is provided at a position lower than the liquid surface Q1of the treatment solution Q contained in the treatment tank 200. Thecontact member 420A is connected to the anode 410R (410L) at a middleposition in the vertical direction, and supplies current to the anode410R (410L), for example.

The contact member 420A is preferably connected to the anode 410R (410L)at a position in the vertical direction that halves the verticaldimension of the workpiece 20 that is suspended from theworkpiece-holding jig 30B. When using a plurality of types of workpiece20 that differ in vertical dimension, the vertical position of thecontact member 420A may be adjusted by utilizing a well-known drivemechanism as the relay current-carrying section 420. Note that thecontact member 420A may come in contact with the anode 410R (410L) overa given length in the direction perpendicular to the sheet.

Current supplied from the contact member 420 flows through the anode410R (410L) in an upward direction E1 and a downward direction E2 fromthe position of the contact member 420 when flowing toward the workpiece20 (i.e., cathode) through the treatment solution contained in thetreatment tank 200. Therefore, current flows through the workpiece 20 toimplement an improved (uniform) current distribution in the verticaldirection.

8. Evaluation of in-Plane Uniformity of Current Distribution

FIG. 17 schematically illustrates the current-carrying paths of theworkpiece-holding jig 30B illustrated in FIG. 13. In FIG. 17, cablesthat are identical in length and cross-sectional area of thecurrent-carrying section are used as the first upper framecurrent-carrying cable 663A, the second upper frame current-carryingcable 663B, the first vertical frame current-carrying cable 671A, andthe second vertical frame current-carrying cable 671B. The resistance ofthe current-carrying path (F1 to F2 in FIG. 17) formed by the firstcurrent-carrying section 660 excluding the first upper framecurrent-carrying cable 663A and the second upper frame current-carryingcable 663B and the resistance of the current-carrying path (F3 to F4 inFIG. 17) formed by the second current-carrying section 670 excluding thefirst vertical frame current-carrying cable 671A and the second verticalframe current-carrying cable 671B are set to be substantially equal toeach other.

The in-plane current distribution of the workpiece 20 was measured usingthe workpiece-holding jig 30B illustrated in FIG. 13 having thecharacteristics schematically illustrated in FIG. 17, and the anode 410L(410R) that employs the current supply method illustrated in FIG. 16.The measurement was performed using wires 700 illustrated in FIG. 18that correspond to the liquid resistance instead of the treatment tank200 illustrated in FIG. 1. As illustrated in FIG. 19, thirty-six contactpoints P provided in the workpiece 20 and thirty-six contact points Pprovided in the anode 410 were respectively connected using the wires700. The positive terminal of a power supply 430 that includes arectifier was connected to the anode 410 at a middle position in thevertical direction through the relay current-carrying section 420, andthe negative terminal of the power supply 430 was connected to thecommon current-carrying sections 301A and 301B of the workpiece-holdingjig 30B illustrated in FIG. 13.

FIG. 20A illustrates the measurement data. FIG. 20B illustrates themeasurement data obtained when using a comparative example in which theworkpiece-holding jig 30A illustrated in FIG. 3 was used instead of theworkpiece-holding jig 30B illustrated in FIG. 13, and current wassupplied to the anode 410 illustrated in FIG. 16 directly from the anodebar 400. As is clear from the comparison between FIGS. 20A and 20B, thein-plane uniformity of the current distribution of the workpiece 20 wassignificantly improved by combining the workpiece-holding jig 30Baccording to one embodiment of the invention and the current supplymethod illustrated in FIG. 16. In particular, while the current valuewas large near the upper end of the workpiece 20 in FIG. 20B(comparative example), a variation in the current distribution of theworkpiece 20 in the vertical direction was significantly reduced in FIG.20A.

Although only some embodiments of the invention have been described indetail above, those skilled in the art will readily appreciate that manymodifications are possible in the embodiments without materiallydeparting from the novel teachings and advantages of the invention.Accordingly, such modifications are intended to be included within thescope of the invention. Any term cited with a different term having abroader meaning or the same meaning at least once in the specificationand the drawings can be replaced by the different term in any place inthe specification and the drawings. The invention also includes anycombinations of the embodiments and the modifications.

For example, the common current-carrying section 301 of theworkpiece-holding jig 30B need not necessarily be used. Acurrent-carrying path from the current-carrying section 340 to the firstchuck members 610 and a current-carrying path from the current-carryingsection 340 to the second chuck members 620 may be separately provided.In this case, independent power supplies may be respectively connectedto the two current-carrying paths.

Although only some embodiments of the invention have been described indetail above, those skilled in the art will readily appreciate that manymodifications are possible in the embodiments without materiallydeparting from the novel teachings and advantages of the invention.Accordingly, all such modifications are intended to be included withinscope of the invention.

Although the invention has been described using specific terms, devices,and/or methods, such description is for illustrative purposes of thepreferred embodiment(s) only. Changes may be made to the preferredembodiment(s) by those of ordinary skill in the art without departingfrom the scope of the present invention, which is set forth in thefollowing claims. In addition, it should be understood that aspects ofthe preferred embodiment(s) generally may be interchanged in whole or inpart.

What is claimed is:
 1. A workpiece-holding jig that vertically holds asheet rectangular workpiece in a solution contained in a treatment tank,and sets the rectangular workpiece as a cathode, the workpiece-holdingjig comprising: a frame member that is disposed to surround therectangular workpiece and includes a conductive upper frame member and aconductive lower frame member electrically insulated from the conductiveupper frame member; a plurality of conductive first clampers that aresupported by the upper frame member, and hold an upper side of therectangular workpiece; a plurality of conductive second clampers thatare supported by the lower frame member in a state in which theplurality of second clampers are electrically insulated from theplurality of first clampers, and hold a lower side of the rectangularworkpiece; a first current-carrying section that supplies current to theplurality of first clampers; and a second current-carrying section thatsupplies current to the plurality of second clampers.
 2. Theworkpiece-holding jig as defined in claim 1, the frame member furtherincluding: two insulating members that are provided on either end of theupper frame member; and two conductive vertical frame members, an upperend of the two vertical frame members being respectively supported bythe two insulating members, and a lower end of the two vertical framemembers being connected to either end of the lower frame member, thefirst current-carrying section supplying current to the upper framemember, and the second current-carrying section supplying current to thetwo vertical frame members.
 3. The workpiece-holding jig as defined inclaim 2, further comprising: a common current-carrying section thatsupports the frame member via part of the first current-carryingsection, and supplies current to the first current-carrying section andthe second current-carrying section.
 4. The workpiece-holding jig asdefined in claim 3, the first current-carrying section including: aninsulating section that is secured on the common current-carryingsection; a conductive connection section that connects the insulatingsection and the upper frame member; and at least one upper framecurrent-carrying cable that connects the common current-carrying sectionand the connection section, and the second current-carrying sectionincluding a first vertical frame current-carrying cable and a secondvertical frame current-carrying cable that connect the commoncurrent-carrying section and the two vertical frame members.
 5. Theworkpiece-holding jig as defined in claim 4, the connection sectionincluding: a first vertical arm section and a second vertical armsection that connect the insulating section and the upper frame member;a first protrusion section that protrudes from the first vertical armsection; and a second protrusion section that protrudes from the secondvertical arm section, and the at least one upper frame current-carryingcable including a first upper frame current-carrying cable that connectsthe common current-carrying section and the first protrusion section,and a second upper frame current-carrying cable that connects the commoncurrent-carrying section and the second protrusion section.
 6. Theworkpiece-holding jig as defined in claim 3, a resistance of a currentpath from the common current-carrying section to the upper frame memberand a resistance of a current path from the common current-carryingsection to the lower frame member being set to be equal.
 7. Theworkpiece-holding jig as defined in claim 5, each of the two insulatingmembers including a guide hole that slidingly guides an upper end ofeither of the two vertical frame members in a vertical direction.
 8. Theworkpiece-holding jig as defined in claim 7, further comprising: aspring that biases either of the two vertical frame member that isslidingly guided by the guide hole in a downward direction.
 9. Theworkpiece-holding jig as defined in claim 8, a lower end of the springbeing secured on either of the two vertical frame members that isslidingly guided by the guide hole, an upper end of the spring beingsecured on a conductive member that is supported by either of the twoinsulating members, and either of the first and second vertical framecurrent-carrying cables being connected to the conductive member.